This invention is related to my copending patent application "A METHOD OF HEAT ASSISTED SHEET METAL FORMING IN 360 DEGREE SHAPES, Ser. No. 95,109, filed concurrently."This application is also related to my copending application, Ser. No. 95,656, filed concurrently and entitled A METHOD FOR FORMING DETAILS AND ADHESIVE BONDING OF SHEET METAL AND COMPOSITE ASSEMBLIES.
2. BACKGROUND--FIELD OF INVENTION
This invention relates to the bonding of shapes for the aerospace and related industries.
2. BACKGROUND--DESCRIPTION OF PRIOR ART
There are factories and subcontractors who produce Bond Assemblies, usually in autoclaves. They have established a history of success in preparing for and producing Sheet Metal Bond Assemblies in autoclaves.
Although they have established a successful history, bonding in an autoclave suffers from a number of disadvantages:
(a) Sheet metal parts of a bond assembly must be placed in or on bond assembly tooling. Bond tools are very expensive. PA0 (b) Adhesive bond assembly details must be bagged and sealed with the tooling in order to pull a vacuum to insure that the bond assembly is pressurized. This is expensive, recurring material cost and requires hand labor. PA0 (c) After placing the bond assembly in the autoclave, it can take a considerable amount of time for the autoclave to come up to temperature resulting in expensive high energy consumption. PA0 (d) It is very difficult to assure an even distribution of temperature within the autoclave and quite often large fans are used to stir the air in an effort to attain said distribution. PA0 (e) Since adhesive bond efficiencies demand that several assemblies be bonded at the same time in an autoclave, it is sometimes necessary to wait until the conditions necessary to bond are met. An example would be if you want a bond cycle of 350.degree. F. at 35 psi and the next cycle is 250.degree. at 70 psi. PA0 (f) Autoclave time must be scheduled. PA0 (a) by using the inner detail as a pressure vessel adhesive bond assemblies, brazed bond assemblies, and other high temperature bond assemblies can be produced in the same facility by adjusting temperature, pressure, and time as appropriate. PA0 (b) to provide controlled heat in a timely manner as the heat source is advantageously located and requires much less energy than the amount used in current facilities. PA0 (c) to avoid the excessive cost of bagging and sealing adhesive bond assemblies for an autoclave as the inner skin is the pressure vessel. PA0 (d) to use the same dies used to form sheet metal or thermoplastic details as bond tools, to insure fit up and eliminate expense of bond tooling. PA0 (e) perforated sheet metal and thermoplastic details can be bonded using the same slave sheet used to form the details. The slave sheet becomes the pressure vessel. PA0 (f) to avoid excessive parts as edge members are incorporated into skins and result in lowest cost and weight. PA0 (g) the facility has incorporated the ability to pull a vacuum on the die side and to use argon on the heater side for bonding in a superclean atmosphere if required.
U.S. Pat. No. 2,416,137 of Auxier and 3,025,208 of Geiger reflect bag molding and an apparatus for adhesive bonding but are very expensive methods of manufacture. My invention deletes-the expense of sealing and bagging for an autoclave.
U.S. Pat. No. 3,072,225 of Cremer on brazed honeycomb sandwich structure is an excellent treatise on brazing. My patent addresses those instances where the inner skin with integral edge closures can be used as the pressure vessel for bonding. The edge closures require attention. See FIG. 18
The lightest possible structures can be bonded in this facility covering a spectrum of temperature from 250.degree. Farenheit to 2000.degree. Farenheit.